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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.config.model.application.provider;

import com.thaiopensource.util.PropertyMap;
import com.thaiopensource.util.PropertyMapBuilder;
import com.thaiopensource.validate.ValidateProperty;
import com.thaiopensource.validate.ValidationDriver;
import com.thaiopensource.validate.rng.CompactSchemaReader;
import com.yahoo.config.application.api.DeployLogger;
import com.yahoo.io.IOUtils;
import com.yahoo.io.reader.NamedReader;
import com.yahoo.yolean.Exceptions;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

import java.io.File;
import java.io.IOException;
import java.io.LineNumberReader;
import java.io.Reader;
import java.io.StringReader;
import java.util.logging.Level;

/**
 * Validates xml files against a schema.
 * Note: Tested by SchemaValidatorTest in config-model module, since
 * needed schema files are in that module
 *
 * @author Tony Vaagenes
 */
public class SchemaValidator {
    private static final int linesOfContextForErrors = 3;

    private final CustomErrorHandler errorHandler = new CustomErrorHandler();
    private final ValidationDriver driver;
    private final DeployLogger deployLogger;

    /**
     * Initializes the validator by using the given file as schema file
     *
     * @param schemaFile schema file
     * @throws IOException if it is not possible to read schema files
     */
    SchemaValidator(File schemaFile, DeployLogger deployLogger) throws IOException, SAXException {
        this.deployLogger = deployLogger;
        this.driver = new ValidationDriver(PropertyMap.EMPTY, instanceProperties(), CompactSchemaReader.getInstance());
        driver.loadSchema(ValidationDriver.fileInputSource(schemaFile));
    }

    public void validate(File file) throws IOException {
        validate(file, file.getName());
    }

    public void validate(File file, String fileName) throws IOException {
        validate(IOUtils.createReader(file.getAbsolutePath()), fileName);
    }

    public void validate(Reader reader) throws IOException {
        validate(reader, null);
    }

    public void validate(NamedReader reader) throws IOException {
        validate(reader, reader.getName());
    }

    private void validate(Reader reader, String fileName) throws IOException {
        errorHandler.fileName = (fileName == null ? "input" : fileName);
        // We need to read from a reader in error handler, so need to read all content into a new one
        Reader newReader = new StringReader(IOUtils.readAll(reader));
        errorHandler.reader = newReader;
        try {
            if ( ! driver.validate(new InputSource(newReader))) {
                // Shouldn't happen, error handler should have thrown
                throw new RuntimeException("Aborting due to earlier XML errors.");
            }
        } catch (SAXException e) {
            // Shouldn't happen, error handler should have thrown
            throw new IllegalArgumentException("XML error in " + errorHandler.fileName + ": " + Exceptions.toMessageString(e));
        }
    }

    private PropertyMap instanceProperties() {
        PropertyMapBuilder builder = new PropertyMapBuilder();
        builder.put(ValidateProperty.ERROR_HANDLER, errorHandler);
        return builder.toPropertyMap();
    }

    private class CustomErrorHandler implements ErrorHandler {
        volatile String fileName;
        volatile Reader reader;

        public void warning(SAXParseException e) {
            deployLogger.logApplicationPackage(Level.WARNING, message(e));
        }

        public void error(SAXParseException e) {
            throw new IllegalArgumentException(message(e));
        }

        public void fatalError(SAXParseException e) {
            throw new IllegalArgumentException(message(e));
        }

        private String message(SAXParseException e) {
            return "Invalid XML according to XML schema, error in " + fileName + ": " +
                    Exceptions.toMessageString(e)
                    + " [" + e.getLineNumber() + ":" + e.getColumnNumber() + "]" +
                    ", input:\n" + getErrorContext(e.getLineNumber());
        }

        private String getErrorContext(int lineNumberWithError) {
            if (!(reader instanceof StringReader)) return "";

            int fromLine = Math.max(0, lineNumberWithError - linesOfContextForErrors);
            int toLine = lineNumberWithError + linesOfContextForErrors;

            LineNumberReader r = new LineNumberReader(reader);
            StringBuilder sb = new StringBuilder();
            String line;
            try {
                reader.reset();
                while ((line = r.readLine()) != null) {
                    int lineNumber = r.getLineNumber();
                    if (lineNumber >= fromLine && lineNumber <= toLine)
                        sb.append(lineNumber).append(":").append(line).append("\n");
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

            return sb.toString();
        }

    }

}